Horn, Patricia2; Santala, Johanna3; Nielsen, Steen Lykke5; Hühns, Maja4; Broer, Inge2; Valkonen, Jari P. T.3
1 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University2 Institute for Land Use, University of Rostock3 Department of Agricultural Sciences, University of Helsinki4 Institute of Pathology, University of Rostock5 Department of Agroecology - Entomology and Plant Pathology, Department of Agroecology, Science and Technology, Aarhus University
Composite plants, with transgenic roots on a non-transgenic shoot, can be obtained by shoot explant transformation with Agrobacterium rhizogenes. The aim of this study was to generate composite potato plants (Solanum tuberosum) to be used as a model system in future studies on root-pathogen interactions and gene silencing in the roots. The proportion of transgenic roots among the roots induced was high (80-100 %) in the four potato cultivars tested (Albatros, Desirée, Sabina and Saturna). No wild-type adventitious roots were formed at mock inoculation site. All strains of A. rhizogenes tested induced phenotypically normal roots which, however, showed a reduced response to cytokinin as compared with non-transgenic roots. Nevertheless, both types of roots were infected to a similar high rate with the zoospores of Spongospora subterranea, a soilborne potato pathogen. The transgenic roots of composite potato plants expressed significantly higher amounts of β-glucuronidase (GUS) than the roots of a GUS-transgenic potato line event. Silencing of the uidA transgene (GUS) was tested by inducing roots on the GUS-transgenic cv. Albatros event with strains of A. rhizogenes over-expressing either the uidA sense or antisense transcripts, or inverted-repeat or hairpin uidA RNA. The three last mentioned constructs caused 2.5-4.0 fold reduction in the uidA mRNA expression. In contrast, over-expression of uidA resulted in over 3-fold increase in the uidA mRNA and GUS expression, indicating that sense-mediated silencing (co-suppression) was not functional in roots. The results suggest that composite plants offer a useful experimental system for potato research, which has gained little previous attention.
Plant Cell Reports, 2014, Vol 33, Issue 12, p. 1977-1992